Barring

This tab appears on the Inbox Properties dialog and itself contains two tabs, Bar mail sent from... and Bar mail addressed to..., entries in which cause Mailtraq to reject incoming messages before downloading them when matching entries are found in the sender or recipient addresses, respectively, in the SMTP envelope.

Mail can be barred based on the sender's email address or based on the email address of the recipient by typing entries, one per line, into the appropriate dialog. The entries are interpreted from top to bottom by Mailtraq.

The message issued by Mailtraq when mail is rejected can be specified in the Message to Send when address is barred edit box.

The address lists in both dialogs support the following placeholders or wildcards, which can be used individually or in conjunction with each other.

*

An asterisk, which represents any sequence of zero or more characters

?

A question mark, which represents any single character

%

A percentage sign, which represents any single number

~

A tilde (ASCII 126), which is used to exclude a wildcard specification

Mail Barring in Mailtraq is implemented in the same way as traditional "bouncing" but with a wider scope and with the addition of sophisticated wildcards. The key feature of Mail Barring during SMTP receipt is that the actual message itself is not downloaded which saves considerable (possibly expensive) on-line time over the alternative methods available, such as deleting the message after receipt.

Mail Barring on Sender or RecipientMailtraq allows mail to be barred by two methods. Firstly by matching the address of the sender, taken from the SMTP MAIL FROM field, against address specifications found in the Bar mail sent from... Tab and, secondly, by matching the address of the recipient, taken from the SMTP RCPT TO field, against address specifications found in the Bar mail sent to... Tab.

The traditional method of barring relies exclusively on barring mail from sender addresses which have previously been identified as responsible for sending abusive messages or junk mail. Although this methodology is successful it should be noted that it is trivial for malicious senders to forge the identity of the sender as it appears in the SMTP MAIL FROM field. Attempting to block all such variations in presented MAIL FROM SMTP envelopes often results in extremely long lists of barred addresses which can prove difficult and time consuming to maintain.

To help overcome this, Mailtraq also implements barring on the identity of the recipient and, properly used, this can provide a very effective defence against junk mail and abusive messages. The most obvious advantage of this method is that the contents of the forward path in messages remains under the control of the user - forged entries in this field means that the message cannot arrive at its intended destination. The major difficulty with this methodology is that the user must have the ability to create alternative mailbox identities within their mail domain and some internet connectivity accounts to do not have this facility.

To make best use of barring on recipient the user should adopt a separate alias, or mailbox name, for each internet activity. For example, a mailing list discussing foobar could be subscribed to using an alias of "foo". If junk mailers obtain that user name and send unwanted mail to it, the name can simply be placed in mail barring after unsubscribing and resubscribing to the mailing list under a different alias.

This practice is also an effective means of identifying the real source of junk mail. If a subscription to a particular service attracts unwanted mail on a regular basis the user has the option of continuing to resubscribe using different aliases or simply discontinuing the activity as not worthwhile. Neither option interferes with mail addressed to other aliases, it should be noted.